Diabetes mellitus is a metabolic disease mainly characterized by a chronic hyperglycemic state caused by a shortage of insulin action. For treating diabetes mellitus, drug therapy is generally practiced together with diet and exercise therapies. For example, a biguanide or thiazolidinedione agent which improves insulin resistance, a sulfonylurea or glinide agent which promotes insulin secretion from pancreatic β cells, or an α-glucosidase inhibitor which inhibits sugar absorption is used as an oral hypoglycemic agent, a type of therapeutic drug for diabetes mellitus.
However, these agents have been reported to have side effects such as: lactic acidosis (biguanide agent); weight gain and edema (thiazolidinedione agent); hypoglycemia and secondary failure due to long-term use (sulfonylurea and glinide agents); and diarrhea α-glucosidase inhibitor). Thus, there is a need to develop an oral hypoglycemic agent that can solve such problems.
Moreover, pyrimidine compounds, piperidine-1-carboxylate compounds, and the like have also been developed in recent years as oral hypoglycemic agents having a novel structure (see e.g., Patent Documents 1 to 4).    Patent Document 1: Pamphlet of International Publication No. WO 05/7647    Patent Document 2: Pamphlet of International Publication No. WO 05/121121    Patent Document 3: U.S. Patent Application No. 2007/167473    Patent Document 4: Pamphlet of International Publication No. WO 07/3962